铷原子气体玻色－爱因斯坦凝聚体的实验和理论研究
文献类型：学位论文
| 作者 | 徐震 |
| 学位类别 | 博士 |
| 答辩日期 | 2009 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 王育竹 |
| 关键词 | 激光冷却 玻色－爱因斯坦凝聚体 光学晶格无序 |
| 其他题名 | Experimental and theoretical study of Bose-Einstein condensate of 87Rb gases |
| 中文摘要 | 自稀薄原子气体中的玻色－爱因斯坦凝聚体（BEC）实现以来，量子简并气体已经成为了冷原子物理中最重要的研究对象。近几年，Feshbach共振和光偶极势（特别是光学晶格）这两项重要的新的量子操控技术的发展拓展了冷原子气体相关的物理研究范围，并产生了一个新的研究领域——量子模拟。 作者在读期间对BEC实验平台进行了改进，其中包括对超高真空系统、激光稳频系统、QUIC磁阱线圈、线圈电流精密控制器、时序系统和成像系统的改进和调试。通过在QUIC阱中的受迫射频蒸发冷却，观测到了87Rb原子气体的BEC相变。通过双分布的出现和自由膨胀过程中纵横比变化这两个实验现象判定发生了BEC相变，相变温度约为300~400 nK，约有1×106个原子，获得的纯凝聚体约2×105个原子。我们发现了雪茄型势阱内原子云的轴向有效半径的变化可以用来判断在紧束缚状态下是否发生了BEC相变。这种BEC相变的判断方法对于无法关断势阱的BEC装置是非常有效的，提供了一个很好的在紧束缚状态下判断BEC相变的依据。我们提出了一种实现一维可控光晶格的方案，并为此制作了一台新型的电光调谐外腔反馈激光器，获得了一些初步的一维可控光晶格的实验结果。我对一维无序光晶格中的BEC行为进行了理论分析和数值计算，针对Maryland大学小组的实验，计算了分数型光晶格的能带结构，通过虚时演化和分步傅立叶变换的方法数值模拟了BEC在一维无序光晶格中的演化过程，分析了无序引起的局域化现象，了解了无序和相互作用等因素对一维光晶格的绝热装载的影响。 |
| 英文摘要 | Since the observation of Bose-Einstein condensate (BEC) in dilute atomic gases, Quantum degenerate gases have been the most important object in cold atom physics. In the past few years, two major new development of the quantum manipulation techniques which are including Feshbach resonance and optical dipole trap, especially optical lattices, have considerably enlarged the range of physics that is accessible with ultracold gases, and have produced a new research regime, quantum simulation. The author have improved the platform of BEC experiment, including modified and tested the UHV system, frequency stabilization of the laser system, the coils of QUIC trap， the precisely controller of the current for these coils, timing system and imaging system. Through the RF enforced evaporative cooling in the QUIC trap, the BEC phase transition of 87Rb atom gases was observed. BEC phase transition was judged by two phenomena that is the appearance of bi-model distribution and the change of aspect ratio with free expansion. The transition temperature is about 300 ~ 400 nK with about 1×106 atoms, about 2×105 atoms have been pure condensated. We found the change of the effective axial radius of the atomic gases in the cigar-shape trap can judge the BEC transition in tight confinement. This kind of indication for BEC transition is very effective for the condition which the trap cannot be shut down completely, and become a useful criterion of BEC transition in tight confinement. We proposed a new method to realize 1D controlled optical lattice, and manufactured a new kind of ECDL laser with EO detuning for this kind of optical lattice, and observed some primary results of 1D controlled optical lattice. The behaviors of BEC in 1D disorder optical lattice have been theoretical analyzed and numerical calculated. For experimental results of the group in Maryland University, the band structures of incommensurable optical lattices were calculated, and the BEC evolution procedure of 1D disorder optical lattice were numerically simulation by imaginary evolution method and split-step Fourier transformation method. Then we analyzed the localization phenomenon due to disorder and realized the influence of disorder, interaction et al, for the adiabatic loading of 1D optical lattice. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15261]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 徐震. 铷原子气体玻色－爱因斯坦凝聚体的实验和理论研究[D]. 中国科学院上海光学精密机械研究所. 2009. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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